It initially detected correctly but it no longer works

tried reinstalling itunes but that did not help.

Detecting ipad or iphone requires a hardware. Maybe that hardware is spoilt.
try looking at this: https://discussions.apple.com/thread...art=0&tstart=0

iTunes is not 100% compatible with Windows 8. I've spent countless hours on this already. I've tried almost everything you can think of. However, using redsn0w I was able to install iOS 5 in Windows 8.

iTunes takes a very long time to load in Windows 8, then when connecting an iPod it takes forever to recognize it's connected, It's hit and miss I've had it connected for over 20 minuets now and it's not showing up , earlier today it connected and updated to version 5.0.1. I'm beginning to wonder if it has anything to do with other programs that may be running. My iTunes is version 10.5 the current version. I'll go to bed tonight and in the morning it will probably show us, that is what happened last night, I was able to eject it normally after it finally displayed in the menu. This is with an iPod Touch, My old iPod 30gb click wheel shows right up when connected.

try this, plug in your apple device when windows 8 is running, then restart your computer. iTunes should start up and recognize your device now